Method of improving oil well drilling muds



Patented Sept. 28, 1937 I 2,094,316 METHOD OF IMPROVING OIL WELL DRILLING MUDS Boy Cross and Matthew Forbes Cross, City, Mo., assignors to Kansas City Laboratory, Kansas City,

of Missouri Kansas Testing Mo., a corporation No Drawing. Application March 6, 1936,

Serial No. 67,530

'1 Claims.

This invention relates to the process of improving oil well drilling muds. It more specifically has to do with the use of mixtures of base exchange zeolites and water to produce oil well drilling mud or to be added to ordinary drilling mud. The usual oil well mud is made from clay or shale like matter obtained locally at the well site. The muds are used in the rotary drilling system in which a cutting tool is fastened to the end of the drill pipe. This drill pipe is hollow and together with the bit or cutting tool, is turned by means of a rotating table at the top of the well. The cuttings instead of being baled out as in the case of drilling with cable tools, are continuously removed. This removal is effected by pumping the drilling fluid down through the drill pipe which is ordinarily about six inches in diameter, out over the bit in the bottom of the well and back on the outside of the drill pipe between the drill pipe and the casing or the wall of the well. The muds for this purpose. must be sufiiciently fluid to be readily pumped and have a sufficient viscosity to wash away the cuttings from the face of the bit and carry them by reason of this viscosity to the top of the well Where they are removed by screens and by sedimentation and the mud is returned to the well. In this circulation, it is necessary that the formations above the bit be sealed off sufiiciently to prevent loss of the water from the drilling mud. In order to effect this sealing off, it is necessary that the mud block the flow of fluid out into the formation and the flow of fluid from the formation. The latter is accomplished by reason of the pressure of the column of liquid in the hole. The first is accomplished by selecting a mud which will properly close the interstices in the particles of the material composing the wall. If the water penetrates the wall of the hole, it will usually cause caving or if the water penetrates to such an extent that it does not come back to the surface of the hole, the head of the liquid is lowered and gas, oil or artesian water under pressure will tend to be released into the hole and the wall will cave and the well will blow out.

When drilling an oil well, it is desirable to drill as much hole as is possible without setting casing to support the wall of the hole. The oil well mud therefore, performs a function of plastering up the side of the wall so that it remains intact while the bit is being sent deeper.

Ordinary muds used in oil well drilling contain from 25% to 40% of total solids and are prone to separate into two layers. They have a tendency to give up the water to the wall of the hole without proper sealing. In such case, a large amount of solids build up which fall back in the hole. It is desirable to seal with the thinnest poseo sible film of colloidal matter or to seal by causing the mud to gel as it passes into the interstices of the wall.

The present invention has to do with the use of selected zeolites or zeolitic clays which have the property of exchanging their bases. The bases may be magnesium, calcium or an alkali such as sodium. By the law of mass action, the sodium will replace the magnesium or calcium to a certain degree when the sodium is present in very high concentrations, for example, in the form of a 10% salt brine. On the other hand, a small concentration of calcium or magnesium will replace the sodium to form calcium zeolite or magnesium zeolite/ As a general thing, the calcium zeolite has less tendency to form a colloidal mixture than the magnesium or sodium zeolite. A calcium zeolite suspension may therefore, be allowed to penetrate a sandstone and when it comes into contact with salt such as occurs in brine, thickens by reason of the formation of sodium or magnesium zeolite.

Certain clays, particularly such as those found in northern Florida, contain a large amount of base exchange zeolite. A lump of this clay when added to water will not form a gel and will not swell as in the case of bentonite. Such a clay will not react with magnesium oxide as does bentonite. However, when passed through a colloid mill either with or without undergoing base exchange activity, it will produce a viscous mixture with from 1 to 10% concentration in water. For example, a 4% mixture when run through a colloid mill will produce a suspension which has a viscosity of from 20 to 100 centipoises as determined by the Stormer viscosimeter. A special clay, for example, such as that obtained from Quincy, Florida, is representative. Four parts of this clay when mixed with 96 parts of water gives a viscosity of 48 when passed through a colloid dispersion mill. The'same mixture when shaken in a shaking machine or an ordinary bottle gives a viscosity of 3; when mixed with a blade stirrer such as a malted milk machine, gives a viscosity of 19.

A typical analysis of this zeolitic clay after air drying is as follows:

. Percent Moisture 2.65 Loss on ignition 9.73 Silica 62.02 Alumina 10.62 Iron oxide 3.60 Lime 1.50 Magnes 8.99 Sulphur; 0.05 Alkalies 0.84

Other zeolites have a largerpercentage of lime or alkalies.

as sodium 7 other suitable, mill to the ultimate particles.

Ordinary clays when dispersed in a colloid mill do not give the viscosity that; is developed with base exchange zeolitic clays. For example, an ordinary kaolin will require 30% or more of solids 7 per 100 grams of mixture to give, a viscosity approximating 'that'of4% Quincy, Florida, base exchange zeolite with 96% water.

The usual viscosity desired: for, oil w ll, drilling mud; is vfrom 5 to 50: centipoises."

may be attained by'a totalsolid'content of base exchange-zeoliteof from 1% to 5%; I

It isv to be understood, however, that this in-, vention is not limited to base exchange'zeolites' of the'above composition. 7

exchange zeolitesjhave a very-3ni1ch larger amount of alumina and a'low'er amount of silica;

For example, natrolite which has been reversed: by alternate treatment; with alkali and magnesium has a proximately the following composi Artificial magnesium zeolite may have the following composition:

Some fullers earth such as at Jamieson, Florida, contain a large percentage of base exchange zeolites. base exchange zeolite may be used in the proportion of from 1% to with water alone to This particular zeolitic clay 1 pre-'- dominates in magnesiai; Magnesia,a1l{ali and I lime mayto a varyingdeg'ree replace each others vIn some 'Zeolitic'clay's such as a typical one from Z -near Ocala, Florida, the lime p redominates. In

this case, to obtain the highest viscosity, the clay should be treated with: alkalies, particularly 2.1-: i

ikalies producing hydroxyl ions such I hydroxide or sodium carbonate. When the clay contains a large amount of i magnesium :zeolite, 'isuch conversion is not necessary or desirable as j the ,magnesiumiseems toconfer considerable vise cosity and permits dispersion in a colloid mill or;

This viscosity clay. 7 y

' 4. A mud ladenfluid for drilling oil and gas .wells containing a zeolitic clay of such natural Some or these i base Asis apparent from the foregoing, the

make a vir'gin foil well mudof viscosityof frorn 5 to 50 centipoise's, dependent upon the quality of f I the zeolite andtypeof base and theparticular 1 result desired. ;Or the zeolite, may be added in small quantities tothe oil well mud already made f I to increase the viscosity or improve its sealing March 11,1936, which has now matured into S. Patent No. 2,044,75v.- I 1 e I claim: I I v 1 1. A mud ladenfiuid for oil or gas wells conthe mixture taining' a colloidally dispersed natural izeolitic clay.

2. A mud laden fluid foroil or gas wells con' taining I a colloidally dispersed, natural zejolitic clay and an alkali.

v 3. The process of improving oil well drilling hand which includes adding to the muda col loidally,dispersedbase exchange natural'zeolitic' particle fineness that when colloidally dispersed in water in quantities thereof less ltha n about f 10% will produce a dispersion having a viscosity 1 I i greater than about 5 centipoises.

s. A mud laden fluid fordrilling Gill a d, gas;

1% to10% viscositygreater than about 5 centipoises. v

1 6. The process of; improving oil well drilling mud which includes adding to the mud a base exchange zeolitic clay of such natural particle fineness thatouantities thereof less than about 10% when colloidally dispersed in water will produce a dispersion having a viscosity greater than about 5 centipoises.

7. The process of improving oil well drilling mud which comprises adding to the mud a natural base exchange zeolitic clay of the Florida- Georgia type, which, when colloidally dispersed in water in quantities-from about 1% to about 5% of the dispersion, will produce a dispersion having a viscosity greater than about 5 centipoises.

ROY CROSS. MATTHEW FORBES CROSS.

wells containing a natural base exchange zeolitic clay of the Florida-Georgia type, which, when w colloidally dispersed in water in quantities of from will produce a dispersion having a 

